Apple has filed for patent on a technology they call an "enforcement routine," that’ll display ads on pretty much any device with a screen and demand that you view them — or else you don’t get your device back:
"Its distinctive feature is a design that doesn’t simply invite a user to pay attention to an ad — it also compels attention. The technology can freeze the device until the user clicks a button or answers a test question to demonstrate that he or she has dutifully noticed the commercial message. Because this technology would be embedded in the innermost core of the device, the ads could appear on the screen at any time, no matter what one is doing.
